This landed in R58 in https://chromium.googlesource.com/chromium/src/+/2512542164d696c21c6a62a0f103e1af9c37ca45

Requesting to merge to R57

Approving merge to M57 Chrome OS.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5fef0127c7d48ef621e3ded6568eabb473ad9d54

commit 5fef0127c7d48ef621e3ded6568eabb473ad9d54
Author: Luis Hector Chavez <lhchavez@google.com>
Date: Thu Feb 16 21:57:03 2017

[Merge-57] arc: Logging ARC data removal reasons

There have been cases where the ARC user data has been requested to be
removed without having a paper trail about the reason why it happened.
This change should provide the reason in the logs so feedback reports at
least can tell what happened.

BUG= 692830 
TEST=cq

Review-Url: https://codereview.chromium.org/2678273005
Cr-Commit-Position: refs/heads/master@{#449047}
(cherry picked from commit 2512542164d696c21c6a62a0f103e1af9c37ca45)

R=yusukes@chromium.org

Review-Url: https://codereview.chromium.org/2705493002 .
Cr-Commit-Position: refs/branch-heads/2987@{#562}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}

[modify] https://crrev.com/5fef0127c7d48ef621e3ded6568eabb473ad9d54/chrome/browser/chromeos/arc/arc_optin_uma.cc
[modify] https://crrev.com/5fef0127c7d48ef621e3ded6568eabb473ad9d54/chrome/browser/chromeos/arc/arc_optin_uma.h
[modify] https://crrev.com/5fef0127c7d48ef621e3ded6568eabb473ad9d54/chrome/browser/chromeos/arc/arc_session_manager.cc
[modify] https://crrev.com/5fef0127c7d48ef621e3ded6568eabb473ad9d54/chrome/browser/chromeos/arc/arc_session_manager.h
[modify] https://crrev.com/5fef0127c7d48ef621e3ded6568eabb473ad9d54/chrome/browser/chromeos/arc/enterprise/arc_enterprise_reporting_service.cc